The solar reflected component in Jupiter's 5-μm spectra from NIMS/Galileo observations
Journal of Geophysical Research: Planets 103:E10 (1998) 23043-23049
Abstract:
A comparison between low-flux dayside and nightside spectra of Jupiter recorded by the Galileo near-infrared mapping spectrometer (NIMS) experiment gives the first accurate estimate of the solar reflected component at 5 μm, in the equatorial zone of Jupiter. A minimum flux level of about 0.6 μW cm-2 sr-1V/μm is found on the dayside, compared with 0.1 /μW cm-2 sr-1/μm on the nightside. These fluxes are 100-800 times lower respectively than the bright 5-μm thermal emission in the north equatorial belt (NEB) hot spots. The day/night difference can be interpreted as a solar reflected component from a cloud, presumably the ammonia cloud, with an albedo of the order of 15%, located at a pressure level of 0.79 bar or at higher altitudes (corresponding to cloud temperature of 160 K or lower). Compared to the measurements in hot spots made at other wavelengths from ground-based observations and from NIMS real time spectra, they imply a high cloud opacity in cold regions at atmospheric levels where the cloud optical depth in the hot spots is very low. The residual flux on the nightside arises from (1) a very small cloud transparency giving some access to deeper thermal emission or (2) as high-resolution solid-state imaging (SSI) images of Galileo suggest, to cloud inhomogeneities, with clearer regions of medium brightness temperatures, mixed with dark regions of much lower thermal emission. If the former have the same brightness as a typical hot spot, a filling factor of a few percent is sufficient to explain the observed flux level on the nightside cold regions. Copyright 1998 by the American Geophysical Union.ISO LWS far-infrared observations of jupiter and saturn
European Space Agency, (Special Publication) ESA SP (1997) 325-328
Abstract:
Portions of the far-infrared spectra of Jupiter and Saturn measured in grating mode with the ISO Long Wavelength Spectrometer (LWS) are presented. The observed Jovian spectrum between 55 and 90 μm is compared to an atmospheric radiative transfer model using expected values for the constituent vertical concentration profiles. Rotational transitions of ammonia are responsible for the absorption features observed against the hydrogen continuum emission. There is good agreement between the model and data for an ammonia mole fraction of 2×10-4 constrained by saturation up to a 75 mbar cut-off, above which it is assumed all the ammonia is destroyed by ultraviolet radiation. Three sections of the saturnian spectrum are compared to synthetic spectra and absorption features due to methane are identified. The mole fraction of methane is constrained between 0.7-1.5 10-3.Temporal and spatial variations in the Venus mesosphere retrieved from Pioneer Venus OIR
Advances in Space Research 19:8 (1997) 1169-1179
Abstract:
Measurements of the Venus mesosphere made in 1978/79 by the Pioneer Venus Orbiter Infrared Radiometer (OIR) have been reanalysed. An optimal estimation retrieval technique has been applied to data from individual orbits. These retrievals reveal the structure of transient features such as the polar dipole and polar collar and short term variations in water vapour abundance and cloud top height. High abundances of water vapour are observed at equatorial latitudes in the early afternoon with a spatial structure which appears consistent with the ultraviolet 'Y' shaped structure. Additionally a two to four day period is observed in both water vapour abundance and cloud top height which is the characteristic period of this ultraviolet feature. © 1997 COSPAR. Published by Elsevier Science Ltd.Radiative transfer models for Galileo NIMS studies of the atmosphere of Jupiter
ADV SPACE RES 19:8 (1997) 1149-1158
Abstract:
Scientific results from NIMS observations of Venus have been extensively reported in the literature, while those of Jupiter have, at the time of writing, just barely commenced. The planning and interpretation of studies of these planets, with their massive atmospheres and exotic compositions (by terrestrial standards), requires a comprehensive treatment of radiative transfer in both. This paper describes work done at Oxford to develop the underlying theory and practical radiative transfer schemes, with particular reference to the NIMS wavelength range, spectral resolution, and scientific objectives for Jupiter. Equivalent work for Venus has already been reported in the literature (e.g. Kamp and Taylor, 1990) and will not be covered in detail here. (C) 1997 COSPAR. Published by Elsevier Science Ltd.ISO LWS measurement of the far-infrared spectrum of Saturn
Astronomy and Astrophysics 315:2 (1996)